Communication of whole genome sequencing (WGS) results to patients is a key ethical and psychosocial issue, but more work has focused on whether to communicate results than how. Young breast cancer patients (diagnosed at d 40 years) are a key population for early application of WGS to identify cancer susceptibility alleles and mutations affecting treatment response, particularly those with a strong family history of breast cancer who do not carry a known BRCA1/2 mutation. However, little is known about their communication preferences regarding the content and delivery of WGS results. Based on an integrated conceptual framework of risk information and processing, we will examine young breast cancer patients' communication preferences for WGS results (i.e., content, delivery format, information source, timing) and factors that may affect these preferences (i.e., genetics-related beliefs, decision-making preferences, breast cancer recurrence worry, informational norms, health literacy). We will recruit all participants through the nationwide Young Women's Breast Cancer Research Program, focusing on four subgroups: those with a strong breast cancer family history and no identified BRCA1/2 mutation; with no identified BRCA1/2 mutation and no or moderate family history; BRCA1/2 mutation and a strong family history; and a strong family history who have not received genetic testing. The specific aims are to: (1) investigate communication preferences for WGS results among young breast cancer patients; and (2) administer a survey to young breast cancer patients in order to examine (A) factors affecting communication preferences for WGS results among young breast cancer patients with a strong family history of breast cancer and no identified BRCA1/2 mutation and (B) compare communication preferences for WGS results among subgroups of young breast cancer patients. We will use a sequential mixed-methods design. For Aim 1, we will conduct qualitative, semi-structured individual interviews with 60 young breast cancer patients, 15 per subgroup, and investigate communication preferences for WGS results. Based on these qualitative data, we will develop a survey for Aim 2. In Aim 2, following cognitive testing of the survey with 12 young breast cancer patients, we will administer the survey online to 865 young breast cancer patients total in the four subgroups. We will examine whether preferences for communication of WGS results vary by genetics-related beliefs, decision-making preferences, breast cancer recurrence worry, informational norms, and health literacy among those with a strong breast cancer family history and no identified BRCA1/2 mutation. We will also compare communication preferences among the four subgroups in order to examine quantitatively the effects of family history, known BRCA 1/2 mutation status, and having had genetic testing. This study is innovative because of its focus on empirical questions related to communication of WGS results among a population relevant to early application of WGS. These findings will be critical in improving patient care by advancing our understanding of how to communicate WGS results to young breast cancer patients.